This invention relates to an ink jet printhead. More particularly, the invention relates to a Drop Flight Correction for Moving Nozzle Ink Jet.
Most ink jet printheads of the type manufactured using micro-electro mechanical systems (MEMS) technology have been proposed in a construction using nozzle chambers formed in MEMS layers on the top of a substrate with nozzle chambers formed in the layers. Each chamber is provided with a movable paddle actuated by some form of actuator to force ink in a drop through the nozzle associated with the chamber upon receipt of an electrical signal to the actuator. Such a construction is typified by the disclosure in my International Patent Application PCT/AU99/00894.
Other constructions may dispense with the paddles and cause ink drops to be forced from the nozzle by decreasing the size of the nozzle chamber. It has been realised that this can be achieved by causing the actuator to move the nozzle itself downwardly in the chamber thereby avoiding the need for a paddle, simplifying construction and providing an environment which is less prone to the leakage of ink from the nozzle chamber.
In both these types of construction, the actuators are typically fixed/free end beam type thermal bend actuators. During operation, these slightly rotate the paddles in the chambers in the first mentioned construction type or the nozzle openings in the second mentioned construction type. Because of the angular displacement of the paddle in the first type of nozzle, the drop may be ejected at a slight angle to the normal of the plane of the opening. Because of the angular displacement of the nozzle opening in the second type of nozzle, the drop may be ejected normal to the plane of the opening, but the normal has angularly displaced along with the opening during the ejection of the drop. This slight angular deviation of the drop is not a potential problem if all the nozzles on the printhead have the same orientation. However, to maximise the packing density of nozzles on the printhead, and thereby reduce manufacturing costs, the nozzles in adjacent rows are oriented such that their actuators extend in opposite directions. Accordingly, the angular deviations in the flight of drops from successive rows are also in opposite directions. This can ultimately have adverse effects on print quality.
According to the invention there is provided an ink jet printhead including a plurality of nozzles each adapted to eject drops of ink through an opening toward a surface to be printed; wherein
the opening is asymmetrical to provide a flight direction of ejected drops that differs from the flight direction provided if the opening were symmetrical.
Preferably, each nozzle has an associated nozzle chamber adapted to be supplied with ink via at least one conduit in an underlying substrate, the nozzle chamber being defined by a floor portion having peripheral sidewall and a roof portion having depending peripheral sidewall, the sidewalls of the floor and roof portion arranged to overlap in a telescopic manner;
said roof portion having said opening formed therein for the ejection of ink drops from said nozzle chamber; and
an actuator arranged to move said roof portion upwardly and downwardly relative to said floor portion, wherein said roof portion tilts relative to said floor portion when moved downwardly by said actuator, and said opening is asymmetrically shaped so as to eject ink drops in a direction other than perpendicular to said roof portion.
Preferably, the nozzle is configured to eject ink in a direction substantially perpendicular to said floor portion.
Preferably, the nozzle is so configured by being provided with a relatively wider portion at the end of the opening proximate the actuator, and a relatively narrower portion at the end of the opening remote from the actuator.
Preferably, the wider portion is flatter in edge configuration than the narrower portion which is relatively more pointed.